The purpose of the response circuit is to show that the AI-2 signalling system can be coupled with a desired response.

Figure 1. Schematic diagram of the response circuit.

The response circuit consists of the qrr4 promoter followed by the c1 lambda inverter (BBa_Q04510) and aiiA (BBa_C0160). This has been designed and constructed so that in the absence of AI-2, the signalling system acts as a phosphorylation cascade that eventually leads to the phosphorylated form of LuxO, which then complexes with a transcription factor. This complex binds to the qrr4 promoter, inducing the expression of the c1λ repressor protein, thus preventing the expression of aiiA. When AI-2 is present, it binds to LuxP and switches the system into a dephosphorylation cascade, leading to the unphosphorylated form of LuxO. Consequently, no binding occurs at the qrr4 promoter, preventing the expression of the c1λ repressor protein. This allows for the expression of aiiA, a gene that encodes an AHL-degrading enzyme allowing us to target biolfim maintenance.

For an in depth look into the construction of the response circuit (complete with results to date) please read the paper below (or click HERE).